Crystallite Size Increase of Silver Nanoparticles by Ligand Exchange and Subsequent Washing Process with Antisolvent

Desorption performance of ligands from silver nanoparticles extremely affects a sintering process of nanoinks for their writing fine pattern. In this study, we investigated desorption behaviors of ligands on the surface of silver nanoparticle through ligand exchange and subsequent washing process with antisolvent. Ligand exchange reactions from oleic acid to tri-n-octylphosphine oxide (TOPO), octanoic acid (OA), and 1-dodecanethiol (DDT) were carried out on the surface of silver nanoparticle. After the washing process with methanol as an antisolvent, their crystallite sizes and the amounts of ligands existing on the particle surface were evaluated by powder X-ray diffraction and thermogravimetric analysis, respectively. In the case of ligand exchange with TOPO, the crystallite size dramatically increased and the amount of ligands existing on the particle surface significantly decreased. This result shows that TOPO is easy to desorb from the silver surface in the washing process with methanol, which resulted in the efficient coalescence of silver. In contrast, the coalescence of silver nanoparticles capped with OA and DDT was less efficient. Moreover, the effect of the antisolvent in the washing process on the coalescence of silver was demonstrated in detail.